It applies notably, but not solely, to the field of underwater surveillance in which one or more sensors, possibly contained in an antenna, are towed by a craft. Optical fibers are conventionally used to feed back measurements obtained by the sensor(s) on board the craft. Optical fibers have the advantage of making it possible to convey data without a significant loss, with a high bit rate of the order of several hundred megabits per second over a significant distance, possibly ranging up to several hundred meters.
A towed antenna or a sensor is conventionally placed in water and brought back on board the craft by way of a winch situated on board the craft. The winch comprises a structure that is fixed to the craft and a drum that is intended to rotate about an axis of the winch with respect to the structure. Feeding back data by way of optical fibers requires equipping the winch with a slip ring for optical fibers. This slip ring makes it possible to transmit the data from a first optical fiber (rotor fiber) linked to the drum rotating about the axis of the winch to another optical fiber (stator fiber) linked to the structure of the winch rotating about the axis of the winch.
A contactless slip ring for optical fibers is known. The contactless slip ring allows contactless data transmission from a fixed part of the slip ring, linked to a stator fiber, to a rotating part of the slip ring, linked to a rotor fiber, so as to allow data communication between the rotor fiber and the stator fiber. The contactless slip ring from the prior art is configured so as to place the stator fiber and the rotor fiber facing one another. Contactless data transmission makes it possible to avoid the problems of transmission degradation linked to the mechanical wear of the components. This solution is simple and relatively inexpensive but limited to a single pair of rotor and stator fibers. For example, it is not suitable for providing multi-fiber data transmission, that is to say from a plurality of optical fibers to a plurality of other optical fibers.
A slip ring comprising a Dove prism interposed between rotor and stator optical fibers, allowing multi-fiber data transmission from two rotor optical fibers to two stator optical fibers, is also known. However, a significant insertion loss is unfortunately present on one of the two optical transmission channels.
Another solution for multi-fiber optical transmission consists of a slip ring comprising, for each rotor fiber-stator fiber pair, an optical/electrical transducer for converting a signal conveyed by a rotor optical fiber into an electrical signal, a capacitive slip ring comprising an electrode linked to the fixed part of the slip ring and an electrode linked to the rotating part, which are coupled capacitively so as to transmit the electrical data from the fixed part to the rotating part of the slip ring, and an electrical/optical converter for converting the electrical data originating from the capacitive slip ring into an optical signal injected into the stator fiber. In this case, the two data transmission channels exhibit limited data transmission losses, but the capacitive slip rings remain expensive.